Atrial natriuretic peptide in children with idiopathic hypercalciuria.

We measured plasma atrial natriuretic peptide (ANP) levels in 30 children with idiopathic hypercalciuria (IH) and 19 normal controls (NC). A calcium (Ca) loading test was performed in all patients to determine the type of IH. Subsequently plasma ANP, cAMP and renin activity (PRA), serum total and ionized Ca, intact parathyroid hormone, aldosterone, and 1,25-dihydroxyvitamin D as well as urine Ca, cAMP, and electrolytes were determined in all subjects. The mean (SD) plasma ANP levels were significantly lower in patients with renal hypercalciuria (RH) [21.4 (4.8) pg/ml] than in those with absorptive hypercalciuria (AH) [26.8 (7.6) pg/ml, P<0.05] and NC [27.6 (6.6) pg/ml, P<0.001]. PRA was significantly lower in AH [2.9 (1.3) ng/ml per hour] than in RH patients [7.8 (6.8) ng/ml per hour, P<0.01] and in NC [6.8 (4.6) ng/ml per hour, P<0.005]. Serum aldosterone values were significantly lower in AH [14.5 (11.4) ng/dl] than in RH patients [25.4 (14.1) ng/dl, P<0.05] and in NC [32.6 (20.5), P<0.001]. The lower plasma ANP levels in RH than in AH patients and in NC may be due to Ca depletion. The lower PRA and serum aldosterone levels in AH than in RH patients and in NC may be attributed to Ca excess.